Vacuum house behind upper intake tends to come off from time to time. I tried to put a clamp on it but the space is really right. Look directly behind the engine intake in the middle and you'll so the hose

Re: Vacuum leak from brake booster

Same happened to me yesterday. A real bugger just to find the vacuum nipple behind the manifold with a mirror and then reconnect the hose. I used a plastic zip-tie as a clamp to secure it better. Hope that holds it for a bit until I can pick up a new hose. Now that the car has over 80K miles on it, it seems some oil breather vapor in the intake has caused the old hose to swell and it no longer fits securely.